linux-kernel - Re: [PATCH] block: xen-blkback: don't get/put blkif ref for each queue

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Message-ID: <20160926141459.GC11534@char.us.oracle.com>
Date:   Mon, 26 Sep 2016 10:14:59 -0400
From:   Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
To:     Bob Liu <bob.liu@...cle.com>
Cc:     xen-devel@...ts.xenproject.org, roger.pau@...rix.com,
        linux-kernel@...r.kernel.org
Subject: Re: [PATCH] block: xen-blkback: don't get/put blkif ref for each
 queue

On Mon, Sep 26, 2016 at 03:36:24PM +0800, Bob Liu wrote:
> xen_blkif_get/put() for each queue is useless, and introduces a bug:
> 
> If there is I/O inflight when removing device, xen_blkif_disconnect() will
> return -EBUSY and xen_blkif_put() not be called.
> Which means the references are leaked, then even if I/O completed, the
> xen_blkif_put() won't call xen_blkif_deferred_free() to free resources anymore.
> 
> Signed-off-by: Bob Liu <bob.liu@...cle.com>

Reviewed-by: Konrad Rzeszutek Wilk <konrad.wilk@...cle.com>
> ---
>  drivers/block/xen-blkback/xenbus.c |    2 --
>  1 file changed, 2 deletions(-)
> 
> diff --git a/drivers/block/xen-blkback/xenbus.c b/drivers/block/xen-blkback/xenbus.c
> index 3cc6d1d..2e1bb6d 100644
> --- a/drivers/block/xen-blkback/xenbus.c
> +++ b/drivers/block/xen-blkback/xenbus.c
> @@ -159,7 +159,6 @@ static int xen_blkif_alloc_rings(struct xen_blkif *blkif)
>  		init_waitqueue_head(&ring->shutdown_wq);
>  		ring->blkif = blkif;
>  		ring->st_print = jiffies;
> -		xen_blkif_get(blkif);
>  	}
>  
>  	return 0;
> @@ -296,7 +295,6 @@ static int xen_blkif_disconnect(struct xen_blkif *blkif)
>  		BUG_ON(ring->free_pages_num != 0);
>  		BUG_ON(ring->persistent_gnt_c != 0);
>  		WARN_ON(i != (XEN_BLKIF_REQS_PER_PAGE * blkif->nr_ring_pages));
> -		xen_blkif_put(blkif);
>  	}
>  	blkif->nr_ring_pages = 0;
>  	/*
> -- 
> 1.7.10.4
>